FIG. 1 is a view schematically illustrating a conventional projector.
Referring to FIG. 1, the conventional projector includes an illumination system 10a including a lamp assembly 11 adapted to irradiate light, an optical engine unit 10 including a synthesizing system 10b for forming an image, a projection lens unit 20 for refracting and diffusing light to form an image on a screen, a suction fan 31 installed on the top of the projector and adapted to intake ambient air, an exhaust fan 32 installed at the rear wall of the projector and adapted to exhaust hot air generated in the interior of the projector to outside, a lower case 30 installed in the rear of the exhaust fan 32 to protect the exhaust fan 32, and an upper case (not shown) adapted to cover the top of the projector and separates the interior of the projector from the external in cooperation with the lower case 30.
Hereinafter, the operation of the conventional projector having the above mentioned configuration will be described briefly. The lamp assembly 11 generates and irradiates the light. The light irradiated by the lamp assembly 11 is projected onto an image formed on the LCD panel of the synthesizing system 10b while being subjected to a refracting or synthesizing process. Thus, the light projected onto the synthesizing system 10b contains an image signal. This light finally forms a picture on the screen after being controlled in its projection direction as it passes through the projection lens unit 20.
The synthesizing system 10b, which is a part of the projector for forming an image, will be described in more detail. The synthesizing system 10b includes an LCD panel for forming an image, and a prism for reflecting or synthesizing light.
The LCD panel includes three LCD panels respectively associated with red (R), green (G), and blue (B) colors. Light beams obtain different color signals as they are projected onto the LCD panels. These light beams are synthesized together by the prism, and then finally projected onto the screen, thereby forming a picture. When the light is projected onto the R, G, and B LCD panels to form images, a large amount of heat is generated at those LCD panels due to the projected light.
The structure of the LCD panel will be described again in association with a cooling configuration thereof. The suction fan 31, which discharges heated air having a high temperature, is attached to the top of the synthesizing system 10b. Without the suction fan 31, the heat is then accumulated in the synthesizing system 10b causing the liquid crystal present in the LCD panel to be boiled. This is generally known as an LCD boiling phenomenon. When the LCD boiling phenomenon occurs, a dark image is displayed on the screen. In severe cases, polarizing plates may be burnt.
In this regard, it is important to properly cool the projector, especially in latest projectors in which an irradiation of strong light is required to form a large and distinct image. In particular, the products of a high luminance corresponding to 200 ANSI lumens, a projector cooling means has became an important factor in determining the quality of products.
The construction of the above-mentioned suction fan 31 of the conventional projector cooling systems and an air flow created by the suction fan 31 will be described in detail.
FIG. 2 is a side view illustrating the installed state of the suction fan in the conventional projector. Referring to FIG. 2, the cooling system includes an upper case 40 for covering the top of the projector to protect the internal parts of the projector. The suction fan 31 is also included in the cooling system. The suction fan 31 is placed below the upper case 40 with a fixed spaced apart from the upper case to suck and exhaust the hot air in the synthesizing system 10b. 
The operation of the above mentioned cooling system used in the conventional projector will be described hereinafter. In order to cool the synthesizing system 10b heated during the operation of the projector, the suction fan 31 placed above the synthesizing system 10b exhausts air in the inside of the synthesizing system 10b. The hot air exhausted by the suction fan 31 is dispersed in the interior of the projector so that it is naturally cooled. Alternatively, the hot air is externally exhausted by the exhaust fan 32. Thus, the cooling of the projector is achieved.
However, the above mentioned conventional cooling system has a problem in that the synthesizing system 10b is inefficiently cooled because hot air present in the synthesizing system 10b dispersed in the interior of the projector after being discharged by the suction fan 31, and then partially introduced again into the synthesizing system 10b. 